In 1991, Sony Corporation in Japan creatively used carbon material as an anode active material of a lithium-ion battery, which brought a revolutionary change to the lithium-ion battery field. Because the lithium-ion battery has many advantages, such as high voltage, small volume, light weight, high specific energy, non-memory effect, non-pollution, small self-discharge and long cycle life and the like, it has been unprecedentedly developed in application of the field of mobile devices, including mobile phones, cameras, notebook computers and other portable electrical appliances. Since twenty-first century, awareness of environmental protection of the human being has been further improved, so that the lithium-ion battery has more potential to be used, and is generally considered as a desirable power supply of mobile appliances, power supply of electric vehicles and storage device of storage power stations in the new century.
But with a trend of miniaturization and longstanding of portable electronic devices, high energy density of the lithium-ion battery for these devices is required greatly, therefore an active material with high specific capacity is applied to the lithium-ion battery field, wherein alloy material is more outstanding one. For the anode active materials, a Solid Electrolyte Interface membrane (SEI membrane) would be formed during the first charging, which consumes a part of lithium ions deintercalated from the cathode active material, eventually resulting in the first coulombic efficiency of the cell less than 100%. For example, the first coulombic efficiency of graphite material is about 90%, while the alloy anode material is much lower, such as silicon anode active material, the first coulombic efficiency of which ranges from 65% to 85%. In order to improve energy density of the cell, the first coulombic efficiency of the cell is required to increase.
In order to obtain a lithium-rich electrode plate improving the first coulombic efficiency of the cell, domestic and oversea experts have carried out extensive researches, and achieved some achievements. Chinese patent application publication No. CN1830110A discloses a lithium-rich electrode plate with details as follows: lithium metal, an anode material and a non-aqueous liquid are mixed to form a slurry, the slurry is coated on a collector, and then the slurry is baked to obtain a lithium-rich electrode plate of a lithium-ion battery, wherein lithium metal particles are mixed into the coating layer. Due to lithium metal present in the coating layer of the electrode plate, the density of the active material in the electrode plate is lowered, connection among active material particles is weakened and electronic resistance is increased; at the same time, although this method can work in lithium-supplement and finally achieve the object of improving the first coulombic efficiency of the cell, the whole production process of the cell must be operated in a drying chamber and meanwhile the lithium metal and the anode material are difficult to be mixed together, thus the production cost is relative high. Chinese patent application publication No. CN1177417A discloses a lithium-rich lithium ion battery with details as follows: a lithium sheet is covered on a surface of an anode electrode plate, and then wound to form a battery; and then an electrolyte is injected, to produce a lithium-rich lithium-ion battery. When applying this method for lithium-supplement, since relative thin lithium metal sheet can not be produced by the existing technology, the quantity of lithium which can be absorbed by the anode electrode plate is much less than that provided by the lithium metal sheet, which results in problems, such as over lithium-supplement, deposition of lithium in the cell, poor cycle performance, and the like.
Therefore, it is necessary to provide a lithium-rich electrode plate of a lithium-ion battery and a preparation method thereof which can effectively control lithium-supplemental quantity to an anode and improve lithium-supplemental uniformity.